Re: [PATCH 2/3] irqchip/gic-v3-its: Zero ITTs reused from the ITT pool

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 06/11/2026 09:26, Fuad Tabba wrote:
> Commit b08e2f42e86b5 ("irqchip/gic-v3-its: Share ITS tables with a
> non-trusted hypervisor") moved sub-page ITTs from kzalloc_node() to a
> genpool. The pages added to the pool are zeroed, but an ITT freed back
> to it goes to the next device as the previous one left it. MAPD is then
> UNPREDICTABLE: "When V == 1, the specified ITT does not contain all
> zeros" (IHI 0069H.b, 5.3.10).
> 
> Zero the ITT when it comes from the pool.
> 
> Fixes: b08e2f42e86b5 ("irqchip/gic-v3-its: Share ITS tables with a non-trusted hypervisor")
> Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
> ---
>   drivers/irqchip/irq-gic-v3-its.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 5613c52adf88e..5c3ab9d30f6af 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -267,8 +267,10 @@ static void *itt_alloc_pool(int node, int size)
>   
>   	do {
>   		addr = gen_pool_alloc(itt_pool, size);
> -		if (addr)
> +		if (addr) {
> +			memset((void *)addr, 0, size);
>   			break;
> +		}

It is safer to do this at allocation than freeing something back to the 
gen_pool.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

>   
>   		page = its_alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
>   		if (!page)